Controlling the position of a cursor is important when using certain types of machines such as a computer or video games. Cursors have been controlled by keyboard keystrokes. Improved ergonomic interfaces include a joystick, mouse and trackball. Using these devices, a computer operator has a better "feel" for adjusting cursor position relative to control operation. However, each of these devices requires the operator to move a physical object which is hard wired to the machine. Such a practice can be cumbersome or inefficient requiring the operator to retrieve and deposit the object for each use.
There are other non-keyboard devices which must be moved for controlling a cursor. These devices include such means measuring the doppler shift, combining infrared and ultrasonic transceivers, transmitting light from a light pen at the display screen, or affixing a radio transmitter or receiver to the head of the user. Such methods and devices are shown in Baker, et al., in U.S. Pat. No. 4,578,764, King et al., in U.S. Pat. No. 4,565,999, Davison, U.S. Pat. No. 4,682,159, Herrington et al., U.S. Pat. No. 4,645,648, and Mueller et al., U.S. Pat. No. 4,550,250.
Lefkowitz, in U.S. Pat. No. 4,524,348, discloses a cordless control interface between a physical object such as a part of the human body, and a machine. Movement of the physical object in a defined field is sensed, and signals corresponding to such movement are received, detected, amplified and produced as an input signal to the machine to move an element of the machine in the same direction as, and in an amount proportional to, movement of the object. In one embodiment, the machine is a video game system and the element is a display signal.
The Lefkowitz apparatus comprises planar antennas, such as sheets of metal and the antenna is coupled to a detunable oscillator. If a physical object, such as a human hand, is placed into the field of the oscillator, the presence of the hand due to body capacitance is communicated to a tuned circuit in the form of added capacitance to the combination of circuit capacitance causing an alteration in the frequency of the active oscillator. Such alteration is in the form of the lowering the operating frequency. Accordingly, the position of the hand is sensed. By moving the hand, the capacitance changes.
The sensed object is electrically coupled as a capacitance into the circuit of Lefkowitz through one or more antennas. The position of an electrically inert object, having no ability to effect the capacitance of the system, cannot be detected and located. Therefore, electrically inert objects cannot be used to control a cursor using Lefkowitz. In certain applications, such as video or computer games, a player may wish to wield an object, such as a sword, baseball bat or the like, to enhance the realism of play. Where such objects are electrically inert for safety or other reasons the object cannot be sensed.
The oscillations are typically in the radio frequency range. Accordingly, these devices are expensive to manufacture. Further, governmental restrictions are placed upon radio frequency devices requiring adherence to government restrictions.
An ideal cordless cursor control device would merely sense the position of any physical object, for example, the operator's hand without requiring the operator to move an object or requiring the use of expensive radio frequency oscillators. Such a device would be extremely easy for the user to operate. Further, such a device would greatly simplify and enhance the playing of video games.